This invention relates to the field of fiber optics illumination systems, and more particularly to illuminators that provide a source of illumination for plastic fiber bundle light guides of the type having a soft pliable polymeric core.
The present invention pertains particularly to flexible plastic fiber light guides or light pipes of the type having a central soft and pliable polymeric core with one or more cladding sleeves applied thereover. A specific example is the plastic flexible light pipe manufactured under the trademark Optiflex by Rohm and Haas Company of Bristal, Pa.
The soft pliable polymeric core is a trade secret composition of Rohm and Haas Company and this core is immediately cladded with a clear Teflon sleeve or sheathing, which in turn is covered with a white plastic cladding.
The advantage of such plastic flexible light pipe is that the light pipe or fiber is extremely flexible when compared to glass fiber and to other stiffer plastic fibers. Accordingly, larger diameter light pipes or fibers may be utilized in the bundle. For example, Rohm and Haas Company manufactures such a flexible light pipe designated as 7100-IEWS light pipe which has a 7 mm diameter light pipe sheathed with a white plastic cladding having an outside diameter of approximately 9 mm.
Such plastic optical fibers are not only desirable to use because of their flexibility and size, but also because of the quality and character of the light transmitted by such light pipes. However, such plastic fiber optics are more susceptible to heat damage than glass fibers. Polymerized fiber optics or light pipes deteriorate quickly when exposed to high heat and oxygen. They turn yellow and then brown if the heat applied to the light receiving distal ends of the fibers is exposed to excessive heat. The proximal fiber ends can also deteriorate and become opaque if exposed to excessive heat.
It is accordingly desirable to maintain the interface between the light pipes and the illuminator at 50.degree. C. or less for such plastic fibers. Various techniques have been used to cool the interface at the light receiving distal ends of the fiber optics bundle, including filters, fans, cold mirrors, masking mirrors with apertures, optical conductor rods and combination lens light couplers.
For example, reference may be had to U.S. Pat. Nos. 5,099,399; 5,259,056 and 5,513,291.
It is a principal object of the present invention to provide an illuminator system for plastic fiber bundle light guides of the aforementioned type manufactured by Rohm and Haas Company which have a soft pliable core wherein the fiber optics interface with the light source is fully protected from dirt, dust, water or other deposits or contaminates to thereby preserve the efficiency of the optical design and to further provide a system which truly maintains an optical fiber interface at less than 50.degree. C.
This particular polymeric flexible light pipe is described as having a "pliable" core. It is observed that in the prior art such a core is sometimes referred to as being a "compressible" core. However, it is preferred to utilize the term "pliable" inasmuch as this term is believed to be more accurate in that the term "compressible" tends to convey that the material can be made more compact by the application of pressure, rather than being soft and pliable or putty like.
A further object of the present invention is to provide such an illumination system which is capable of transmitting light through such elongated light pipes with exceptional efficiency whereby an average light projection from the distal ends of the fibers can be expected of at least 150 lumens with expectations of even achieving a maximum in excess 190 lumens of transmitted light from each fiber.